Impact sound transmission

Impact sound transmission tests are carried out using a standard
tapping machine that incorporates 5 steel-faced hammers. These are driven by a motor so they
strike the floor being tested 10 times per second. The tapping machine is placed in several
positions on the floor and the impact sound pressure levels are measured in the room below in
the frequency range 100 to 3150 hertz. The details of the machine and the measurement
procedures are described in ASTM E492, Standard Test Method for Laboratory Measurement of
Impact Sound Transmission through Floor-ceiling Assemblies using the Tapping Machine. The
sound pressure levels are used to calculate IIC as described in ASTM E989, Standard
Classification for Determination of Impact Insulation Class (IIC).

To obtain the single-number ratings, a reference contour is used in a
procedure that is analogous to that for Airborne Sound
Transmission Loss. The contour extends from 100 to 3150 Hz. The measured 1/3 octave band
impact sound pressure levels are fitted to the contour subject to the following rules:

Deviations occur when a measured value (red bars) is greater than the contour (blue
line).

The contour is adjusted until sum of deviations <=32. For IIC, no individual
deviation may be greater than 8 dB.

The IIC value is read from the contour value at 500 Hz using the right hand
axis.

The IIC rating increases as the impact sound insulation improves.

Impact insulation can also be measured in buildings according to ASTM E1007, Standard
Test Method for Field Measurement of Tapping Machine Impact Sound Transmission through
Floor-ceiling Assemblies and Associated Support Structures. The test procedure and
calculations are essentially the same as E492, the laboratory test, but the rating is called
Field Impact Insulation - FIIC